Vane comprising a transition zone

ABSTRACT

A vane of a guide vane or impeller blade of a turbo machine, particularly a gas turbine. The profile of the vane includes at least one thickening that is advantageous for flow purposes in a radially inward final region and/or a radially outward final region of the vane. The thickening is cut in the area of a forward edge of the vane so as to form a mirror surface or a basal plane.

The present invention relates to a blade of a guide vane or of a rotor blade of a fluid flow machine according to the definition of the species set forth in claim 1. The present invention also relates to a fluid flow machine according to the definition of the species set forth in claim 13.

The European Patent EP 0 798 447 B1 describes a blade for fluid flow machines, in particular for gas turbines, which extends radially in a ring channel or flow channel, adjacently to at least one defining side wall of the ring channel, the blades exhibiting a thickened portion of the blade profile that is beneficial from a standpoint of fluid mechanics. In accordance with the EP 0 798 447 B1, this thickened portion is formed by an enlarged leading-edge nose radius and/or an enlarged leading-edge wedge angle and/or an enlarged trailing-edge wedge angle and/or an enlarged absolute profile thickness of profile sections adjacent to the defining side wall, as compared to a reference profile section. By employing blades having this type of design, guide vanes, as well as rotor blades, and, respectively, guide vane rings as well as rotor blade rings can be provided whose blade geometry influences a secondary flow in order to minimize the blade losses. However, the drawback associated with such a blade geometry is that the thickened portion necessitates an increased overall axial length of the blade and thus, ultimately, of the entire fluid flow machine.

Against this background, the object of the present invention is to devise a novel type of blade of a guide vane or of a rotor blade of a fluid flow machine.

This objective is achieved by a blade as set forth in claim 1. In accordance with the present invention, the thickened portion is cut in the area of one leading edge of the blade, forming a mirror surface or a basal plane.

It is provided along the lines of the present invention for the or each thickened portion of a blade to be cut in the area of one leading edge of the blade, forming a mirror surface or a basal plane. As a result, the decisive advantage is derived over the related art that secondary flow losses are minimized without having to elongate the overall axial length of the blades and thus of the fluid flow machine. In this respect, the present invention makes it possible to achieve a compact design of the fluid flow machine, while, at the same time, minimizing the secondary flow losses in the fluid flow machine.

In accordance with one advantageous embodiment of the present invention, a straight or plane cut is made in the thickened portion, in the area of the leading edge, in such a way that the cutting direction of the cut extends circumferentially or transversely to the axial direction of the fluid flow machine.

One alternative advantageous embodiment of the present invention provides for a circular segment-shaped or cylindrical segment-shaped cut to be introduced into the thickened portion in the area of the leading edge in such a way that a tangent line placed at the frontmost portion of the cut extends circumferentially or transversely to the axial direction of the fluid flow machine.

The or each thickened portion is preferably formed by a large radius of curvature at the radially inside end region and/or at the radially outside end region of the blade, the ratio of the radius of curvature to a chord length of the blade being between 2% and 10%.

The fluid flow machine according to the present invention is defined in independent claim 13.

Preferred embodiments of the present invention are derived from the dependent claims and from the following description. The present invention is described in greater detail in the following on the basis of exemplary embodiments, without being limited thereto. Reference is made to the drawing, whose figures show:

FIG. 1: a blade according to the related art in a highly schematized, perspective side view;

FIG. 2: the blade according to FIG. 1 as viewed in the direction II of FIG. 1;

FIG. 3: a blade according to the related art in a representation analogous to FIG. 2;

FIG. 4: a section through the blade of FIG. 3 in the cross-sectional view taken along direction III-III;

FIG. 5: a blade according to the present invention in a highly schematized, perspective side view;

FIG. 6: the blade according to FIG. 5 as viewed in the direction VI of FIG. 5;

FIG. 7: a second blade according to the present invention in a representation analogous to FIG. 6; and

FIG. 8: a third blade according to the present invention in a representation analogous to FIGS. 6 and 7.

Prior to describing the present invention in greater detail with reference to FIG. 5 through 8, a few of the interrelationships known from the related art will first be discussed with reference to FIG. 1 through 4.

FIG. 1 shows a blade 10 of a rotor blade known from the related art in a highly schematized, cutaway view, on a radially inside, hub-side end region, blade 10 of rotor blade according to FIG. 1 having a thickened portion 11 of the blade profile that is beneficial from a standpoint of fluid mechanics. In this context, thickened portion 11 extends in accordance with FIG. 2 all around the blade profile of blade 10, thus both on an intake side, as well as on a thrust side of blade 10 between a leading edge 12 and a trailing edge 13 thereof. In accordance with FIG. 3, characteristic parameters of blade 10, i.e., of the blade profile, include chord length 1 of the blade which is defined by the distance between leading edge 12 and trailing edge 13, as well as maximum profile thickness dMAX of the blade.

In accordance with FIG. 1 through 4, thickened portion 11 is achieved at the hub-side end of blade 10 of the rotor blade (not shown in greater detail) by providing a hub-side profile section of blade 10 with an absolute profile thickness d greater than a reference profile section, the contour of thickened portion 11 in accordance with FIG. 4 being defined by a radius of curvature r. A thickened portion 11 of this kind makes it possible to minimize secondary flow losses.

It should be noted here that thickened portion 11 shown in FIG. 1 through 4 merely represents one possible variant of secondary flow-minimizing thickened portions. Other secondary flow-minimizing thickened portions can be obtained by increasing the profile parameters leading-edge nose radius and/or leading-edge wedge angle and/or trailing-edge wedge angle and/or absolute profile thickness. With respect to the details pertaining to such thickened portions, reference is made to the European Patent EP 0 798 447 B1, whose disclosure is explicitly incorporated by reference herein.

It should also be noted here that, in the case of rotor-mounted rotating rotor blades, the blades are provided with such thickened portions 11 only on the radially inside, hub-side end. On the other hand, if it is a question of fixed guide vanes, then, typically, they each have a thickened portion 11 of this kind, both on the radially inside, hub-side end, as well as on the radially outside, housing-side end.

The present invention provides for thickened portion 11 to be cut in the area of leading edge 12 of blade 10, forming a mirror surface 14 or a basal plane. This is illustrated in particular in FIG. 5. In the exemplary embodiment of FIGS. 5 and 6, a straight or plane cut is made in thickened portion 11, in the area of leading edge 12, in such a way that the cutting direction of the cut extends circumferentially (arrow 15) to the fluid flow machine. As may be inferred from FIG. 6, in this case, the thus formed plane mirror surface 14 extends in parallel to circumferential direction 15. In other words, in order to produce plane mirror surface 14, the cutting direction extends in this case transversely and, respectively, perpendicularly to the axial direction (arrow 16) of the fluid flow machine.

In the exemplary embodiment of FIGS. 5 and 6, as described in connection with FIG. 1 through 4, thickened portion 11 is configured to extend around the blade and is characterized by a large radius of curvature r at the radially inside end region and, respectively, at the radially outside end region of the blade; along the lines of the present invention, radius of curvature r being dimensioned in such a way that the ratio of radius of curvature r to chord length 1 of blade 10 is between 2% and 10%, preferably between 4% and 8%, and most preferably between 5% and 7%. The ratio of radius of curvature r to chord length 1 is preferably 6%.

The combination of a thickened portion having large radius of curvature r and the cutting of thickened portion 11 in the area of leading edge 12, forming a mirror surface 14, makes it possible to minimize secondary flow losses without having to elongate the overall axial length of the blade or of the fluid flow machine.

FIG. 7 shows another exemplary embodiment of a blade 10 according to the present invention, in the exemplary embodiment of FIG. 7 as well, blade 10 having a thickened portion 11 at the radially inside, hub-side end region and/or at the radially outside, housing-side end region, thickened portion 11, in turn, being cut in the area of leading edge 12, forming a mirror surface 17. In contrast to the exemplary embodiment of FIGS. 5 and 6, in the exemplary embodiment of FIG. 7, instead of a plane cut, a circular segment-shaped or cylindrical segment-shaped cut is introduced into thickened portion 11 in the area of leading edge 12. The circular segment-shaped or cylindrical segment-shaped cut is introduced into thickened portion 11 in such a way that a tangent line 18 placed at the frontmost portion of the cut or of resulting mirror surface 17 extends in parallel to the circumferential direction (arrow 15), as well as transversely or perpendicularly to the axial direction (arrow 16) of the fluid flow machine.

Common to the exemplary embodiment according to FIG. 7 and to that according to FIG. 5 and 6, is that radius of curvature r of thickened portion 11 is constant over the entire blade profile of blade 10. In contrast, FIG. 8 shows a blade 10 designed in accordance with the present invention, having a variable radius of curvature r, which diminishes from leading edge 12 toward trailing edge 13 of the blade. As is inferable from FIG. 8, blade 10 is cut at leading edge 12, again forming a mirror surface or basal plane, in the exemplary embodiment of FIG. 8, just as in the exemplary embodiment of FIG. 7, a circular segment-shaped or cylindrical segment-shaped cut being executed to form mirror surface 17. By employing a variable radius of curvature r in the area of thickened portion 11, secondary flow losses may again be minimized.

The blades according to the present invention are preferably used for guide vanes or rotor blades of a turbine or of a compressor of a gas turbine, in particular of a gas turbine aircraft engine. As previously mentioned, the blades of rotating rotor blades have thickened portions in accordance with the present invention merely in the area of the hub-side end. Fixed guide vanes may have a thickened portion of this kind both on the radially inside, hub-side end, as well as on the radially outside, housing-side end. In accordance with the present invention, the thickened portions are cut in the area of the leading edge, forming a mirror surface or a basal plane. The present invention also provides for a large radius of curvature to be used. This makes it possible, on the one hand, to minimize secondary flow losses without, on the other hand, having to increase the overall axial depth or length of the fluid flow machine equipped with such blades. 

1-14. (canceled)
 15. A blade of a guide vane or of a rotor blade of a fluid flow machine comprising: at least one thickened portion of the blade profile beneficial from a standpoint of fluid mechanics on a radially inside end region and/or on a radially outside end region of the blade, the thickened portion having a cut in an area of a leading edge of the blade forming a mirror surface or a basal plane.
 16. The blade as recited in claim 15 wherein the cut is a straight or plane cut.
 17. The blade as recited in claim 16 wherein the cut in such a way that a cut direction of the cut extends circumferentially or transversely to an axial direction of the fluid flow machine.
 18. The blade as recited in claim 15 wherein the cut is a circular segment-shaped or cylindrical segment-shaped cut.
 19. The blade as recited in claim 18 wherein cut has a tangent line at a frontmost portion extending circumferentially or transversely to the axial direction of the fluid flow machine.
 20. The blade as recited in claim 15 wherein the blade is a blade of a guide vane, the thickened portion being formed in each case at a radially inside, hub-side end region and at a radially outside, housing-side end region of the blade.
 21. The blade as recited in claim 15 wherein the blade is a rotor blade, the thickened portion being formed at a radially inside, hub-side end region.
 22. The blade as recited in claim 15 wherein the at least one thickened portion is formed by a large radius of curvature at the radially inside end region and/or at the radially outside end region of the blade, a ratio of the radius of curvature to a chord length of the blade being between 2% and 10%.
 23. The blade as recited in claim 22, wherein the ratio of the radius of curvature to the chord length of the blade is between 4% and 8%.
 24. The blade as recited in claim 23, wherein the ratio of the radius of curvature to the chord length of the blade is between 5% and 7%.
 25. The blade as recited in claim 22 wherein the radius of curvature is designed to be variable to diminish from the leading edge toward a trailing edge of the blade profile.
 26. The blade as recited in claim 15 wherein the at least one thickened portion is formed by increasing at least one profile parameter of a leading-edge nose radius and/or a leading-edge wedge angle and/or a trailing-edge wedge angle and/or an absolute profile thickness, as compared to a contour of a reference profile section.
 27. A gas turbine comprising a blade as recited in claim
 15. 28. A fluid flow machine comprising: at least one guide vane ring having a plurality of guide vanes and at least one rotor blade ring having a plurality of rotor blades, the guide vanes and the rotor blades each having blades that extend in the radial direction of a flow channel, and, at a radially inside end region and/or at a radially outside end region of the blade, the blades exhibiting a thickened portion of the blade profile that is beneficial from a standpoint of fluid mechanics, the thickened portion having a cut in an area of a leading edge of the blade forming a mirror surface or a basal plane.
 29. The fluid flow machine as recited in claim 28 wherein the fluid flow machine is a gas turbine.
 30. The fluid flow machine as recited in claim 28 wherein the cut is a straight or plane cut.
 31. The fluid flow machine as recited in claim 28 wherein the cut is a circular segment-shaped or cylindrical segment-shaped cut.
 32. The fluid flow machine as recited in claim 28 wherein the at least one thickened portion is formed by a large radius of curvature at the radially inside end region and/or at the radially outside end region of the blade, a ratio of the radius of curvature to a chord length of the blade being between 2% and 10%.
 33. The fluid flow machine as recited in claim 28 wherein the at least one thickened portion is formed by increasing at least one profile parameter of a leading-edge nose radius and/or a leading-edge wedge angle and/or a trailing-edge wedge angle and/or an absolute profile thickness, as compared to a contour of a reference profile section.
 34. The fluid flow machine as recited in claim 28 wherein the blade is a blade of a guide vane, the thickened portion being formed in each case at a radially inside, hub-side end region and at a radially outside, housing-side end region of the blade.
 35. The fluid flow machine as recited in claim 28 wherein the blade is a rotor blade, the thickened portion being formed at a radially inside, hub-side end region. 